When passing through the town of Fishguard, the road width thru the town and
especially Lower Fishguard is a very narrow only single lane road
leading to many traffic issues especially with HGVs. Articulated
HGVs have been recently banned from this section between Fishguard and Dinas Cross because of
the difficulties of HGVs passing other traffic on this section.

There was a by-pass built around the town of Cardigan during 1989/90 which consists of a
new concrete bridge of the River teifi followed by a 3 lane road up
the hill to the north of the town.

The section of road in the Dulas valley between the Afon Dyfi near Machynlleth and Corris was built in the 1840s at
the instigation of the local slate quarry owners to replace the old
turnpike road on the opposite side of the
valley. It may have utilised part of the formation of the Roman Sarn Helen. From 1859 the
road was kept company on this section by the narrow-gauge Corris
Railway.

Between Penrhyndeudraeth and Porthmadog, the road passes over a
mile-long embankment, known as "The Cob". Until 2003, drivers had
to pay a charge to cross The Cob.

The section between Porthmadog and Llanwnda has been improved. The new
section bypasses Llanllyfni and Penygroes, in parts utilizing the
old trackbed of the Caernarfon to Afon Wen railway
line. In April 2007, the 10-mile new section had to be resurfaced
in its entirety after it became apparent that the wrong type of
stone had been used for the surface tarmac.